CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2005

  • question_answer
    If AM and GM of\[x\]and y are in the ratio\[p:q,\]then\[x:y\]is:

    A)  \[p-\sqrt{{{p}^{2}}+{{q}^{2}}}:p+\sqrt{{{p}^{2}}+{{q}^{2}}}\]

    B)  \[p+\sqrt{{{p}^{2}}-{{q}^{2}}}:p-\sqrt{{{p}^{2}}-{{q}^{2}}}\]

    C)  \[p:q\]

    D)  \[p+\sqrt{{{p}^{2}}+{{q}^{2}}}:p-\sqrt{{{p}^{2}}+{{q}^{2}}}\]

    E)  \[q+\sqrt{{{p}^{2}}-{{q}^{2}}}:q-\sqrt{{{p}^{2}}-{{q}^{2}}}\]

    Correct Answer: B

    Solution :

    According to question, \[\frac{x+y}{2\sqrt{xy}}=\frac{p}{q}\] \[\Rightarrow \]               \[\frac{{{(x+y)}^{2}}}{4xy}=\frac{{{p}^{2}}}{{{q}^{2}}}\]                 ?..(i) On subtracting both sides by 1, we get \[\Rightarrow \]               \[\frac{{{(x-y)}^{2}}}{4xy}=\frac{{{p}^{2}}-{{q}^{2}}}{{{q}^{2}}}\]               ?. (ii)     From Eqs. (i) and (ii), we get \[{{\left( \frac{x+y}{x-y} \right)}^{2}}=\frac{{{p}^{2}}}{{{p}^{2}}-{{q}^{2}}}\] \[\Rightarrow \]               \[\frac{x+y}{x-y}=\frac{p}{\sqrt{{{p}^{2}}-{{q}^{2}}}}\] \[\Rightarrow \]               \[\frac{2x}{2y}=\frac{p+\sqrt{{{p}^{2}}-{{q}^{2}}}}{p-\sqrt{{{p}^{2}}-{{q}^{2}}}}\] (by componendo-dividendo rule) \[\therefore \]\[x:y=(p+\sqrt{{{p}^{2}}-{{q}^{2}}}):(p-\sqrt{{{p}^{2}}-{{q}^{2}}})\]


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